Cutting a thread

Honest John Back Room » Technical matters
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Mon 2 Jul 2007 14:24
Cutting a thread - Chris M
I need to repair the armrest on my car. The alloy casting has snapped, but I think I can repair it by drilling and tapping and then using a small bolt, either 5mm or 6mm. What size drill bit should I use for either size? I'm guessing about 4mm or 5mm respectively, but I will only have the one chance to get it right, so one of you more technical types are sure to know!

I'm quite looking forward to the job, as it's been 30 years since my metalwork classes at school (My favourite lesson - Grade A @ O'level).
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Mon 2 Jul 2007 14:33
Cutting a thread - Dynamic Dave
You need a 3.3mm drill for a 4mm tap.
You need a 4.2mm drill for a 5mm tap.
You need a 5.0mm drill for a 6mm tap.

www.simetric.co.uk/sidrill.htm

As it's in aluminium, you might want to consider helicoiling it instead.
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Mon 2 Jul 2007 14:45
Cutting a thread - Chris M
Thanks for the link.
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